9
One of the main features of this release is the addition of reference-counted
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data buffers to Libav and their use in various structures. Specifically, the
11
data buffers used by AVPacket and AVFrame can now be reference counted, which
12
should allow to significantly simplify many use cases. In addition,
13
reference-counted AVFrames can now be used in libavfilter, avoiding the need
14
for a separate libavfilter-specific frame structure. Frames can now be passed
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straight from the decoders into filters or from filters to encoders.
17
These additions made it necessary to bump the major versions of libavcodec,
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libavformat, libavdevice, libavfilter, and libavutil, which was accompanied by
19
dropping some old deprecated APIs. These libraries are thus not ABI- or API-
20
compatible with the previous release. All the other libraries (libavresample
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and libswscale) should be both ABI- and API-compatible.
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Another major point is the inclusion of the HEVC (AKA H.265, the successor of
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H.264) decoder in the main codebase. It was started in 2012 as a Libav Google
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Summer of Code project by Guillaume Martres and subsequently completed with
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the assistance of the OpenHEVC project and several Libav developers.
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As usual, this release also contains support for other new formats, many smaller
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new features and countless bug fixes. We can highlight a native VP9 decoder,
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with encoding provided through libvpx, native decoders for WebP, JPEG 2000, and
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AIC, as well as improved WavPack support with encoding through libwavpack,
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support for more AAC flavors (LD - low delay, ELD - enhanced low delay), slice
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multithreading in libavfilter, or muxing chapters in ASF. Furthermore a few new
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filters have been introduced, namely compand, to change audio dynamics, framepack,
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to create stereoscopic videos, asetpts, to set audio pts, and interlace, to convert
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progressive video to interlaced. Finally there is more fine-grained detection of
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host and target libc, which should allow better portability to various cross
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compilation scenarios.
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See the Changelog file for a fuller list of significant changes.
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Please note that our policy on bug reports has not changed. We still only accept
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bug reports against HEAD of the Libav trunk repository. If you are experiencing
44
issues with any formally released version of Libav, please try a current version
45
of the development code to check if the issue still exists. If it does, make
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your report against the development code following the usual bug reporting
9
With this release we are trying to answer the numerous calls from our users for
10
shorter development cycles. From now on we will aim for approximately two major
13
Libav 11 is API-, but not ABI-compatible with the previous major release. This
14
means that the code using our libraries needs to be rebuilt, but no source
15
changes should be required. Note however, that a number of old APIs remain
16
deprecated and will be dropped in the near future. All users are strongly
17
encouraged to update their code as soon as possible. The doc/APIchanges file in
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the Libav source tree and the migration guide on the wiki should help with
19
migration to the new APIs. If those are not sufficient, do not hesitate to
20
contact us on IRC or through the user mailing list.
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One specific API issue in libavformat deserves mentioning here. When using
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libavcodec for decoding or encoding and libavformat for demuxing or muxing,
24
the standard practice was to use the stream codec context (AVStream.codec) for
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actual decoding or encoding. There are multiple problems with this pattern
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(the main one is that the decoder/demuxer or encoder/muxer are not necessarily
27
synchronized and may overwrite each other's state), so it is now strongly
28
discouraged and will likely be deprecated in the future. Users should instead
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allocate a separate decoding or encoding context and populate it from the
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demuxing codec context (or the reverse for encoding) with the
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avcodec_copy_context() function.
33
The main highlights of this release include native Opus, VP7, OpenEXR, and On2
34
AVC decoders, HEVC encoding through libx265, new APIs for exporting ReplayGain
35
and display transformation metadata and countless bug fixes. A large effort was
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also expended on internal cleanups which are not very visible to our users,
37
but should make the codebase cleaner, safer and easier to maintain and extend.
38
One point worth mentioning is refactoring the large monolithic framework for
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architecture-specific codec optimizations into small blocks, which reduces the
40
size of configurations that selectively enable or disable certain codecs.
42
The avserver streaming tool, which has not been maintained for many years and
43
was mostly broken, was removed from the tree. It was decided that it is a
44
significant maintenance burden and that we do our users no service by pretending
45
to support it, while we in fact do not.
47
See the Changelog file for a more extensive list of significant changes.
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53
have been deprecated and are scheduled for removal in the next release.
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54
Significant API changes include:
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+ added the reference-counted buffers API (buffers.h)
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+ moved the AVFrame struct to libavutil and added a new API for working with
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reference-counted AVFrames (frame.h)
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+ added an API for working with reference-counted AVPackets (av_packet_*)
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+- converted VDPAU to the hwaccel framework; the old way of using VDPAU is no
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- old audio encoding and decoding APIs removed
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- old video encoding API removed
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- deprecated enum CodecID removed (enum AVCodecID should be used instead)
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- deprecated audio resampling API removed (libavresample should be used
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+- replaced AVFilterBufferRef with AVFrame; AVFilterBufferRef and everything
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related to it still exists, but is deprecated
75
+ converted all filters to use the AVOptions system for configuration, it is
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now possible to query the supported options, their values and set them
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directly with av_opt_*
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+ added a slice multithreading framework
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+- merged avfiltergraph.h to avfilter.h, using AVFilterGraph is now explicitly
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mandatory (it was implicitly required even before); added new API for
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allocating and initializing filters
57
+ Added the avcodec_copy_context() function that must from now on be used for
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freeing codec contexts.
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+- Added a new VDA hardware acceleration API, since the old one was broken and
60
not fixable in a compatible way. Deprecated the old VDA API.
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+ Added support for exporting stream-global (as opposed to per-packet) side
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data. This feature is now used by some demuxers to export ReplayGain or
65
display transformation matrix (aka rotation) or stereoscopic 3D mode.
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+ Added an API for live metadata updates through event flags.
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+- Changed the way to provide a hint about the desired timebase to muxers.
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Previously it was done by setting AVStream.codec.time_base. Now callers
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should set AVStream.time_base.
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+ Added an API for working with AVFrames.
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74
Please see the file doc/APIchanges for details along with similar
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75
programmer-centric information.
added
removed
doc/RELEASE_NOTES
